On the Thermal Expansion of Nanoparticles

Magnetite nanoparticles with an average particle size of 7.5 nm were studied by Mössbauer spectroscopy in the 100–300 K temperature range. Using experimental data on the temperature variation of isomer shifts in the partial spectra of ⁵⁷Fe nuclei in the A and B crystal sublattices, the linear thermal expansion coefficient of the ultradisperse magnetite particles in the temperature range studied was estimated within the framework of the molecular orbital formalism: α=(1.2±0.2)×10^‑4K^‑1.